Odd Resistors Values

[Nikon1975]

Dear All,

For an application I am working on, I need some resistors of odd values between 10 and 35 ohm. Something like 32.1 ohm 12.4 ohm. I know they exist as they are installed on the devices, but I cannot find anywhere to buy them. Do you by chance have a source of them ?

Regards,

Davide

 

[schiirrn]

Just parallel two to reach the desired value.

 

[dhaen]

There are online tools to reduce effort eg:
Reverse engineered resistor calculator resistor pairs - search of R1 and R2 with known total resistance iteration resistor calculation - sengpielaudio Sengpiel Berlin

 

[MarcelvdG]

12.4 is an E96 value and should be in stock at any large component supplier, 32.1 is not an E96 and not even an E192 value. I think series or parallel connections is the only practical way to get 32.1 ohm, unless you need thousands of them and can order special values. If you can accept a percent of inaccuracy on top of the tolerance and drift, you can round it to 32.4 ohm, the nearest E96 value.

 

[Nikon1975]

This is the list of values I would need:

18.6
32.5
31.2
12.8
19.0
15.6
17.2
32.6
15.4
16.5
19.6
35.4
23.2

Parallel resistors is a last resort, as these are on a cable in a tight space. Mouser and Digikey do not have most of them, unless I order 10000 pieces.
For my application dissipation is not an issue, but they should be very stable with temperature.

Thanks,

D.

 

[scottjoplin]

Have you considered filing to increase resistance?

 

[Vovk Z]

Something like 32.1 ohm 12.4 ohm. I know they exist as they are installed on the devices, but I cannot find anywhere to buy them.

You can look for that kind of nominals as "0.1%" tolerance ones (or better, "0.05%" ets).

 

[RJM1]

What tolerance do you need? You can get a 32.0 ohm 0.5% resistor for your 32.1 ohm and it
will be within the 0.5% ( 0.16 ohm) tolerance of the 32 ohm resistor.

 

[Monte McGuire]

You can also buy a close value and measure units until you find a resistance close to what you want. You have no control over the actual parts and their values, but if you find suitable parts, you will end up with something proven to be the value you want.

Faceplate values are often merely 'serving suggestions' and actual values will differ. Find an E96 that's close and measure them.

 

[nigelwright7557]

I have designed a few USB scopes and some of the gain resistor values are horrible.
I can get close to most values but some turn out to be silly money at RS Components.
While it doesn't look pretty or take minimal space I sometimes have to resort to series or parallel combinations.

 

[Vovk Z]

You can also buy a close value and measure units until you find a resistance close to what you want. You have no control over the actual parts and their values, but if you find suitable parts, you will end up with something proven to be the value you want.

I have to remember that this way can be good if you have aged 5%-10% resistors. If not - they will "age" and change value of about 0.5%-1.0% with time.
So, precision components (0.1%) are much better with stability.
But there is a possibility with non-precision components too - we can artificially age them by thermocycling (roast at about 100-120 C degrees).

 

[Kay Pirinha]

Have you considered filing to increase resistance?

I wouldn't recommend that, 'cause power capability would be decreased to an uncertain value.
Best regards!

 

[JMFahey]

Dear All,

For an application I am working on, I need some resistors of odd values between 10 and 35 ohm. Something like 32.1 ohm 12.4 ohm. I know they exist as they are installed on the devices, but I cannot find anywhere to buy them. Do you by chance have a source of them ?

Regards,

Davide

Check Mouser and similar large suppliers.

They carry E96 series resistors (1%) ; 12.4 is a standard value; 32.1 is not (there) but 32.4 is and less than 1% away.

And they might have actual 32.1 too if REALLY needed .

That said, I bet you must have some Europe based suppliers too.